JP2003205460A - Cerium oxide-based abrasive regeneration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the polishing speed substantially equal to that before use with the regenerated cerium oxide-based abrasive and low generation frequency of scratch by regenerating a cerium oxide-based abrasive, that is, sufficiently removing glass (silicon) component adhering to the surface of abrasive without cohesion of cerium oxide-based abrasive in the process of regeneration. <P>SOLUTION: A dispersant is added to deteriorated cerium oxide-based abrasive suspension, and then alkali component is added so that the hydrogen ion concentration of the suspension is pH 10.5 or higher. The thus obtained material is heated to 50°C or higher to dissolve the adhering silicon component, thereby regenerating cerium oxide-based abrasive. By the added dispersant, cohesion of abrasive particles can be prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a cerium oxide-based abrasive containing cerium oxide as a main component, which is used for mirror-polishing a glass disk for a magnetic disk, a crystal wafer, a glass for a liquid crystal panel and the like. Regarding

[0002]

2. Description of the Related Art With the widespread use of computers, liquid crystal displays, mobile phones and the like, the amount of glass materials used such as glass disks, crystal wafers and liquid crystal panels is increasing. It is essential that the surface of these glass materials be polished to a mirror surface, and for this purpose, a cerium oxide-based polishing agent containing cerium oxide as a main component is used. While being repeatedly used for polishing, this polishing agent deteriorates and the desired polishing rate cannot be maintained. Most of the deteriorated cerium oxide-based abrasives are currently treated as industrial waste, but from the viewpoints of resource depletion, environmental protection, polishing cost reduction, etc., these abrasives are recycled. It is becoming more desirable to do so.

As a prior art example of such a technique, Patent No. 3
No. 134189 and Japanese Patent Laid-Open No. 6-254764 can be mentioned.

In the technique disclosed in the above-mentioned Japanese Patent No. 3134189, since a large amount of alkali component is added after adding a flocculant to condense a solid content, coarse abrasive grains are inevitably added to the regenerated abrasive. To remain. Therefore, in the case of the abrasive regenerated by this method, there is a problem that scratches are likely to occur on the object to be polished.

The technique disclosed in Japanese Unexamined Patent Publication No. 6-254764 is a method in which an electrolyte is added to a polishing liquid to solubilize the basic components removed by polishing, and at the same time, the polishing abrasive grains in the polishing liquid are precipitated. Since a large amount of electrolyte is added, the polishing abrasive particles agglomerate, and coarse abrasive particles remain in the polishing agent after regeneration. Therefore, scratches are likely to occur on the object to be polished in the same manner.

[0006]

All of these are caused by the agglomeration of the abrasive during the abrasive regeneration process, and the agglomerated abrasive particles cause scratches. It is also possible, but expensive, to remove the agglomerated abrasive particles.

As a result of intensive studies to solve these problems, the present invention can sufficiently remove the glass (silicon) component adhering to the surface of the polishing agent without agglomerating the polishing agent during the regeneration treatment. The inventors have found a method capable of doing so, and by using the regenerated cerium oxide-based abrasive, it is possible to maintain a polishing rate substantially equal to that before use and a low scratch occurrence frequency.

[0008]

The above-mentioned problems can be solved by the following means. That is, the first means for solving the problem is to add a dispersant to a deteriorated cerium oxide-based abrasive suspension, and then to adjust the hydrogen ion concentration of the suspension to pH 10.
Add an alkaline component so that it becomes 5 or more, and add 50
It is a method for regenerating a cerium oxide-based abrasive, which comprises regenerating the cerium oxide-based abrasive by heating it to a temperature of ℃ or more.

A second means of solving the problem is to add a dispersant and an alkaline component so that the hydrogen ion concentration becomes pH 10.5 or more, to the deteriorated cerium oxide abrasive suspension.
A cerium oxide-based abrasive reclaiming method is characterized in that the cerium oxide-based abrasive is regenerated by heating it to a temperature of 50 ° C. or higher.

A third means of solving the invention is characterized in that, in the cerium oxide abrasive regenerating method of the first or second invention, oxycarboxylic acid or polyacrylic acid is added as the dispersant. And a method for regenerating a cerium oxide-based abrasive.

A fourth aspect of the present invention is to provide a method for regenerating a cerium oxide-based abrasive according to any one of the first to third aspects, wherein the alkali component is sodium hydroxide, potassium hydroxide or carbonic acid. It is a method for regenerating a cerium oxide-based abrasive characterized by using sodium, potassium carbonate, or an aqueous solution thereof.

A fifth aspect of the invention is to solve the cerium oxide-based abrasive reclaiming method according to any one of the first to fourth aspects of the invention, wherein after the heating, coarse particles of cerium oxide are produced, and A method for regenerating a cerium oxide-based abrasive characterized by removing a silicon component dissolved in the alkaline aqueous solution.

A sixth means for solving the problem is a cerium oxide-based abrasive regenerating method for regenerating a cerium oxide suspension deteriorated by a polishing operation, wherein the deteriorated abrasive is added by a dispersant. PH of hydrogen ion is 8.5
The first step of keeping the pH at 10.5 and storing without drying, the abrasive suspension stored in the first step is recovered, and a dispersant is further added to the recovered abrasive suspension. Second step for redispersing the polishing agent, adding an alkaline component to the polishing agent suspension in which the polishing agent is redispersed in the above second step to adjust the pH to 10.5 or higher, and adjust the temperature to 50 ° C or higher. A third step for heating, a fourth step for removing coarse particles from the abrasive suspension that has undergone the third step, and
A method for regenerating a cerium oxide-based abrasive comprising a fifth step for removing a silicon component dissolved in an alkaline aqueous solution from an abrasive suspension having undergone the fourth step.

According to a seventh aspect of the present invention, in the method for regenerating a cerium oxide abrasive according to the sixth aspect, the fourth step and the fifth step are performed in reverse order. This is a method for regenerating a cerium-based abrasive.

An eighth aspect of the present invention is a cerium oxide-based abrasive characterized by being regenerated by the cerium oxide-based abrasive regeneration method according to any one of the first to seventh inventions. .

According to a ninth aspect of the invention, a polishing agent suspension regenerated by the cerium oxide-based polishing agent regeneration method according to any one of the first to seventh aspects is further dried. Is a cerium oxide-based abrasive.

[0017]

DETAILED DESCRIPTION OF THE INVENTION In many cases, a suspension of fine particles of cerium oxide is used as an abrasive for mirror-polishing glass and quartz. Since cerium oxide does not have a high hardness, it does not physically or mechanically grind the object to be polished like ordinary abrasives (for example, aluminum oxide). It is believed that when they come into contact with each other, the silicon component chemically reacts and adheres to the cerium oxide to cause a polishing action.

Therefore, as the polishing is repeated, the surface of the cerium oxide fine particles is covered with the adhering silicon component, and the polishing ability is gradually lost, that is, deteriorated. Therefore, it is considered that the polishing ability is recovered by removing the attached silicon component from the surface.

The silicon component adhering to the surface of the cerium oxide fine particles can be dissolved / removed by a strong alkaline solution, and the higher the hydrogen ion concentration pH, the higher the dissolution rate. On the other hand, it is generally considered that aggregation does not easily occur when the hydrogen ion concentration is high. However, it was found that when cerium oxide fine particles were brought into contact with a high-concentration alkaline aqueous solution in order to dissolve the silicon component, cerium oxide was apt to agglomerate when the concentration and the hydrogen ion concentration exceeded a certain level. .

In the present invention, a high-concentration alkali component is used in the process of dissolving the silicon component. However, by adding a dispersant to the deteriorated cerium oxide abrasive in advance, it becomes extremely difficult for the abrasive to aggregate. Controlled by.

According to the present invention, a polishing factory or a polishing workshop for polishing a work such as glass or crystal and a recycling factory or a recycling workshop for regenerating a deteriorated polishing agent are separated from each other. Is in mind. In a polishing factory, a large number of polishing devices are installed to process a large amount of workpieces, the deteriorated polishing agent that appears at that time is stored, and the deteriorated polishing agent is transported to a recycling factory every fixed period or fixed amount. .

[0022] deteriorated cerium oxide based polishing agent, during the storage, and left stationary, inevitably tends to aggregate because it does not undergo stirring action. Further, if partial drying occurs during this period, the particles are more likely to aggregate. To prevent this aggregation, first
In the process, a dispersant is added to the deteriorated cerium oxide-based polishing agent so as to maintain the hydrogen ion concentration pH at 8.5 to 10.5, and it is stored so as not to dry by sealing or the like. The first step is not required when the storage period is short (for example, the regeneration process is performed immediately).

The deteriorated cerium oxide-based abrasive stored in the first step is conveyed to a recycling factory for a certain period or every time a certain amount is stored. Here, it is regenerated through the following second to sixth steps.

In the second step, a dispersant is further added so that aggregation does not occur when the silicon component is dissolved in the next third step. The addition of the dispersant in the second step is essential unlike the addition of the dispersant in the first step, and is oxycarboxylic acid or polycarboxylic acid, more specifically, lactic acid, malic acid, tartaric acid, citric acid, hydroxy. Izobutyric acid and the like can be used. These dispersants can also be added as salts such as alkali metal salts and ammonium salts.

In the third step, the hydrogen ion concentration is adjusted to pH 1
A strong alkali component is added to the cerium oxide-based abrasive to which the dispersant is added in the second step so that the temperature becomes 0.5 or more, and the temperature is heated to 50 ° C. or more. The heating time is required to be 2 hours or more, preferably 3 to 5 hours, and it is desirable to maintain the concentration of the abrasive during the reaction in the range of 5 to 40 wt%. In the third step, the silicon component attached to the cerium oxide-based abrasive particles reacts with the alkaline aqueous solution and is eluted into this aqueous solution. At this time, the dispersant added in the second step can substantially suppress the occurrence of aggregation.

The addition of the dispersant in the second step can be performed simultaneously with the addition of the alkali component in the third step. This is because the reaction rate at which the silicon component elutes and the agglomeration rate are very slow, and thus the dispersant exhibits the effect even faster than these rates.

As the alkali component, sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate can be used, and these are preferably used as an aqueous solution.

In the fourth step, the agglomerated abrasive,
Foreign substances such as dust mixed in in the polishing process and coarse particles such as abrasive cloth fibers that have fallen off are removed. To remove coarse particles,
Water sprinkling method, centrifugal separation method, filtration method with a filter, etc.
They can be used alone or in combination.

In the fifth step, the silicon component eluted in the alkaline aqueous solution in the third step is removed by an arbitrary removing method such as a decantation method. The order of the fourth step and the fifth step may be reversed.

The cerium oxide-based abrasive that has undergone the fifth step is
The adhered silicon component and the mixed coarse particles are removed and regenerated. Therefore, although it is in a wet state, it can be used as an abrasive by diluting it to an appropriate concentration or adding a new abrasive. Further, wet pulverization may be performed in order to make the particle size distribution of the cerium oxide-based abrasive uniform. Further, the cerium oxide-based abrasive may be supplied in a dry state, that is, a powder form, which is a usual supply form.

The sixth step is a drying step for this purpose,
After this step, the normal supply form is achieved.

Examples will be shown below. The specs and polishing conditions of the mirror polishing apparatus used in this example and comparative example are shown below.

Polishing device: S manufactured by Speed Huam Co., Ltd.
H-24 type surface plate rotation speed: 60 RPM Pressure plate rotation speed: 60 RPM Polishing cloth: SUBA400 (manufactured by Rodel Nitta Co.) Surface pressure: 200 g / cm ² Polishing composition flow rate: 60 ml / min Polishing agent concentration: 15 wt% Polishing time: 10 Minute Polishing agent: CO-85 Polishing sample: 3-inch quartz crystal wafer Polishing rate: Calculated from the weight difference between the wafers before and after polishing Polishing surface evaluation: Observing haze, pits, and scratches visually with a concentrating lamp Cerium oxide system Deteriorated state of the polishing agent: When the polishing rate reaches about 60% of the initial polishing rate.

* Example 1 First step: After being used for polishing, the concentration of the deteriorated polishing agent was 20 w.
A 10% aqueous sodium carbonate solution was added to the t% CO-85 slurry to adjust the hydrogen ion concentration to pH 10.2.

Second step: 3 kg of the slurry whose hydrogen ion concentration was adjusted in the first step was dispensed into a 5 liter stainless beaker. Next, with stirring, 50 g of a 5% aqueous sodium tartrate solution was added.

Third step: 10% in the slurry of the second step
100 g of an aqueous sodium carbonate solution was added with stirring to adjust the hydrogen ion concentration to pH 11.5. 7 with stirring
Heated to 0 ° C. and left for 3 hours.

Fourth step: After cooling, 5 μm is obtained by the water sluice method.
Coarse particles of m or larger were removed.

Fifth step: The slurry of the fourth step was allowed to settle, the polishing agent was allowed to settle, the supernatant was removed, and the same amount of pure water was added. This operation was repeated 4 times to complete the regeneration.

* Example 2 First step: After being used for polishing, the deteriorated polishing agent concentration was 20 w.
A 10% aqueous sodium hydroxide solution was added to the t% CO-85 slurry to adjust the hydrogen ion concentration to pH 10.2.

Second step: 3 kg of the slurry whose hydrogen ion concentration was adjusted in the first step was dispensed into a 5 liter stainless beaker. Next, with stirring, 40 g of a 5% trisodium citrate aqueous solution was added.

Third step: 10% in the slurry of the second step
100 g of an aqueous sodium carbonate solution was added with stirring to adjust the hydrogen ion concentration to pH 11.5. 5 with stirring
Heated to 0 ° C. and left for 5 hours.

Fourth step: After cooling, 5 μm is obtained by a water sluice method.
Coarse particles of m or larger were removed.

Fifth step: The slurry of the fourth step was allowed to settle, the polishing agent was allowed to settle, the supernatant was removed, and the same amount of pure water was added. This operation was repeated 4 times to complete the regeneration.

Comparative Example 1 A CO-85 slurry having a deteriorated abrasive concentration of 20 wt% was diluted to 15 wt% and used.

* Comparative Example 2 First step: After being used for polishing, the concentration of the deteriorated polishing agent was 20 w.
A 10% aqueous sodium hydroxide solution was added to the t% CO-85 slurry to adjust the hydrogen ion concentration to pH 10.2.

Second step: 3 kg of the slurry whose hydrogen ion concentration was adjusted in the first step was dispensed into a 5 liter stainless beaker. No dispersant was added.

Third step: 10% in the slurry of the second step
100 g of an aqueous sodium carbonate solution was added with stirring to adjust the hydrogen ion concentration to pH 11.5. 5 with stirring
Heated to 0 ° C. and left for 5 hours.

Fourth step: After cooling, 5μ by a water sluice method.
Coarse particles of m or larger were removed.

Fifth step: The slurry of the fourth step was allowed to settle, the polishing agent was allowed to settle, the supernatant was removed, and the same amount of pure water was added. This operation was repeated 4 times to complete the regeneration.

The results are shown in the table below. Item CO-85 (New) Example 1 Example 2 Comparative Example 1 Comparative Example 2 Polishing rate (μm / min) 0.88 0.90 0.86 0.54 0.90 Scratch (book) 0 0 0 3 8

Comparative Example 1 shows polishing in a state of "deteriorated" with a polishing rate of about 60% with respect to a new abrasive CO-85. Comparative Example 2 is an example of the case where the dispersant was not added in the second step, and it can be seen that with this abrasive, the polishing rate is recovered but the occurrence frequency of scratches is high. From this, it is understood that in Comparative Example 2, agglomeration occurs in the third step and scratches occur when this is used as an abrasive, that is, regeneration is not sufficiently performed.

In Examples 1 and 2, the occurrence of scratches was not recognized and the polishing rate was substantially recovered. Therefore, addition of a dispersant prevented aggregation and sufficient regeneration. I understand.

A sixth step may be added to the above-mentioned Examples 1 and 2, and the regenerated cerium oxide-based abrasive may be dried into a powder form which is a usual supply form. By supplying this polishing agent to the polishing factory, the polishing factory can carry out the polishing work as usual by replacing it with a new dry cerium oxide-based polishing agent or by mixing it with it. .

[0054]

According to the present invention, the glass (silicon) component adhering to the surface of the polishing agent can be sufficiently removed without agglomerating the polishing agent during the regenerating treatment, and the regenerated cerium oxide-based polishing can be carried out. Even if the agent is used, it is possible to maintain a polishing rate substantially equal to that before use and a low scratch occurrence frequency.

Claims (9)

[Claims] 1. A dispersant is added to a deteriorated cerium oxide-based abrasive slurry, and then an alkaline component is added so that the hydrogen ion concentration of the suspension becomes pH 10.5 or more,
A method for regenerating a cerium oxide-based abrasive, which comprises regenerating the cerium oxide-based abrasive by heating it to a temperature of 50 ° C. or higher. 2. A dispersant and an alkaline component are added to the deteriorated cerium oxide-based abrasives suspension so that the hydrogen ion concentration becomes pH 10.5 or higher, and the mixture is heated to a temperature of 50 ° C. or higher to oxidize the suspension. A method for regenerating a cerium oxide-based abrasive, which comprises regenerating a cerium-based abrasive. 3. The cerium oxide-based abrasive reproducing method according to claim 1 or 2, wherein oxycarboxylic acid or polyacrylic acid is used as the dispersant. How to play. 4. The method for regenerating a cerium oxide abrasive according to claim 1, wherein the alkaline component is sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or water. A method for regenerating a cerium oxide-based abrasive, which comprises using an aqueous solution of sodium oxide, potassium hydroxide, sodium carbonate, and potassium carbonate. 5. The method for regenerating a cerium oxide-based abrasive according to any one of claims 1 to 4, wherein after the heating, the generated coarse particles of cerium oxide are dissolved in the alkaline aqueous solution. A method for regenerating a cerium oxide-based abrasive characterized by removing a silicon component. 6. A method for regenerating a cerium oxide-based abrasive for regenerating a cerium oxide suspension deteriorated by a polishing operation, comprising adding an alkali component and / or a dispersant.
The first step of keeping the hydrogen ion concentration at pH 8.5 to pH 10.5 and storing without drying, the abrasive suspension stored in the first step is recovered, and the recovered abrasive suspension A second step for adding a dispersant to the liquid to redisperse the polishing agent, and adding an alkaline component to the polishing agent suspension in which the polishing agent has been redispersed in the second step to have a pH of 10.5 or more, This 5
Third step for heating at a temperature of 0 ° C. or higher, fourth step for removing coarse particles from the abrasive suspension after the third step, and abrasive suspension after the fourth step A method for regenerating a cerium oxide-based abrasive, comprising a fifth step for removing a silicon component dissolved in an alkaline aqueous solution from the above. 7. The method for regenerating a cerium oxide-based abrasive according to claim 6, wherein the fourth step and the fifth step are performed in reverse order. 8. A cerium oxide-based polishing agent which is regenerated by the cerium oxide-based polishing agent reclaiming method according to any one of claims 1 to 7. 9. A cerium oxide-based slurry prepared by further drying the abrasive suspension regenerated by the method for reclaiming a cerium oxide-based abrasive according to any one of claims 1 to 7. Abrasive.